KR101123904B1 - Polypropylene resin composition and molded article prepared therefrom - Google Patents

Abstract

The present invention relates to a polypropylene resin composition, in particular (A) isotactic index (II, Isotactic Index) of 97% or more high crystalline α-olefin-propylene copolymer, and (B) high melt strength polypropylene resin It relates to a polypropylene resin composition comprising and a molded article produced therefrom.

The present invention provides a polypropylene resin composition for plastic caps having excellent heat resistance and abrasion resistance by improving rigidity and wear resistance, and molded articles having excellent physical properties using the same.

Polypropylene, highly crystalline α-olefin-propylene copolymer, high melt strength polypropylene resin, cap, stiffness, wear resistance

Description

POLYPROPYLENE RESIN COMPOSITION AND MOLDED ARTICLE PREPARED THEREFROM}

The present invention relates to a polypropylene resin composition, and more particularly to a polypropylene resin composition for producing a plastic cap excellent in rigidity and wear resistance, and a molded article produced using the same.

Due to the expansion of interest in environmental aspects and recycling, plasticization of bottle cap materials used for various beverage containers is being progressed. Currently, metals and plastics are being used in parallel, but in the case of metals, consumers do not separate the containers and the lids well, and there is a problem that additional sorting equipment is required for recycling.

Accordingly, the development of bottle cap materials using plastics that can replace metals is being actively carried out. In particular, the processability, mechanical properties, appearance, durability and economy are excellent, and technologies using polyolefin-based resins suitable for recycling are actively developed. It is becoming. Among them, polypropylene resin is excellent in formability and chemical resistance and has excellent mechanical properties for the price. Therefore, it is widely used in automobile application parts, home appliances, or food containers. -Olefin-propylene copolymers and propylene-ethylene random copolymers. Of these, propylene homopolymers and α-olefin-propylene copolymers are applied for cap materials of non-acidic beverages.

In particular, cap materials for carbonated beverages and juice containers other than non-carbonated beverages must be excellent in pressure resistance, rigidity and heat resistance, and must have excellent wear resistance to prevent productivity degradation due to snow generation in the mold during the manufacturing process. .

However, simply using a polypropylene homopolymer or an α-olefin-propylene copolymer as in the past cannot achieve sufficient physical properties such as rigidity and abrasion resistance to produce a cap material for a carbonated beverage and a juice container.

Therefore, there is a need for a study on the development of a polypropylene resin composition that can secure physical properties such as stiffness and wear resistance improved enough to be used for cap materials for carbonated beverages and juice containers.

An object of the present invention is to provide a polypropylene resin composition for plastic caps excellent in rigidity and wear resistance.

Another object of the present invention is to provide a molded article comprising the polypropylene resin composition.

The present invention provides a polypropylene resin composition comprising (A) a highly crystalline α-olefin-propylene copolymer having an Isotactic Index (II) of 97% or more, and (B) a high melt strength polypropylene resin. .

The present invention also provides a molded article prepared from the polypropylene resin composition.

Hereinafter, the present invention will be described in more detail.

The present invention is to solve the problem that the physical properties could not be secured sufficient for the production of caps for carbonated beverages and juice containers in the existing polypropylene composition, effectively the high crystalline α-olefin-propylene copolymer and high melt strength polypropylene resin By mixing it can ensure excellent rigidity and wear resistance, it is characterized in that the moldability of the plastic cap manufactured therefrom can be improved.

In particular, the polypropylene resin composition of the present invention comprises (A) a high crystalline α-olefin-propylene copolymer having an isotactic index (II) of 97% or more, and (B) a high melt tension polypropylene resin. Can be

Hereinafter, the respective components of the polypropylene resin composition of the present invention will be described in more detail.

(A) Highly crystalline α-olefin-propylene copolymer

The highly crystalline α-olefin-propylene copolymer has an isotactic index (II) of at least 97%, preferably at least 99%, and has such high stereoregularity, thereby providing rigidity, pressure resistance, and heat resistance. This excellent molded article can be produced. In particular, general polypropylene has an II (Isotactic Index) value of less than 97% or 95% to 96%, but the high crystalline polypropylene of the present invention has an isotactic index (II) value of 97% or more, Productivity can be improved by increasing rigidity and increasing crystallization temperature compared to catalyst products.

The high crystalline α-olefin-propylene copolymer is not limited to one prepared through a specific process, for example, by injecting propylene into a polymerization reactor and injecting triethyl aluminum, a phthalate catalyst imparting high crystallinity, and a silane-based electron donor And a slurry bulk polymerization is carried out at a reaction temperature of 65 ~ 75 ℃ and 32 ~ 34 atm to prepare a high crystalline polypropylene homopolymer, and may be prepared through a process such as performing a copolymerization reaction with ethylene.

At this time, the isotactic index (I.I) in the high crystalline α-olefin-propylene copolymer may be formed corresponding to the isotactic index (I.I) of the polypropylene homopolymer.

The amount of the α-olefin of the α-olefin-propylene copolymer is preferably 4 to 8% by weight, more preferably 5 to 7% by weight. The α-olefin content is preferably 4% by weight or more to reduce impact strength and prevent cracking of the product after molding, and to use 8% by weight or less to secure improved rigidity and heat resistance along with excellent impact strength. desirable.

In addition, the melt index of the α-olefin-propylene copolymer resin may be 2 to 10 g / 10 min, and preferably 2 to 3 g / 10 min or 6 depending on the application, that is, depending on the extrusion molding machine to be applied. To 8 g / 10 min. However, when the melt index is less than 2 g / 10min, the moldability and productivity of the product may deteriorate. When the melt index exceeds 10 g / 10min, the melt strength in the extrusion process of the product is not uniform uniform parison formation The failure rate may increase.

The content of the α-olefin-propylene copolymer may be 70 to 95% by weight, preferably 80 to 90% by weight based on the total resin composition. The content of the α-olefin-propylene copolymer is preferably 70% by weight or more in terms of improving flowability and processability of the prepared resin, and 95% by weight or less in terms of improving wear resistance and melt tension.

(B) high melt strength polypropylene resin

The polypropylene composition of the present invention is characterized by being able to produce a molded article excellent in rigidity, pressure resistance, and heat resistance by including a high melt strength polypropylene resin together with the high crystalline α-olefin-propylene copolymer.

In the present invention, the high melt strength polypropylene resin is a resin having a strain hardening index (SHI) of a physical property value sufficient to obtain the effect of melt tension, for example, a stretch hardening degree of 30 or more, preferably Means having a property value of 60 or more.

In general, polypropylene (PP, polypropylene) resin is widely used in various applications because it is relatively excellent in physical properties such as tensile strength, flexural strength. However, due to the linear structure of the polypropylene chain, the melt tension during melting tends to drop sharply with increasing temperature.

Accordingly, the high melt strength polypropylene resin of the present invention has a higher molecular weight distribution after extrusion to increase melt tension by appropriately mixing high molecular weight polypropylene and low molecular weight polypropylene than when extruded into a single polypropylene using an organic peroxide. Can be to be. At this time, an organic peroxide having a very short half-life may be added to produce long side chain structures and crosslinked structures without decomposing polypropylene, thereby further improving rigidity and wear resistance.

By effectively blending the high melt strength polypropylene resin having improved rigidity and wear resistance into the α-olefin-propylene copolymer resin as compared with the conventional polypropylene resin, it is possible to improve rigidity and wear resistance and to improve processability during the extrusion process.

The melt index of the high melt strength polypropylene resin may be 0.3 to 10 g / 10 min, preferably 1 to 3 g / 10 min. When the melt index of the high melt strength polypropylene resin is less than 0.3 g / 10min, gel formation may occur in the product, resulting in poor productivity, and when the melt index of the high melt strength polypropylene resin is less than 10 g / 10min, it may be difficult to satisfy the physical properties required for the product. .

The flexural modulus of the high melt strength polypropylene resin is 16,000 kgf / cm ² to 20,000 kgf / cm ² , preferably 17,000 kgf / cm ² to 19,000 kgf / cm ² . When the flexural modulus of the high melt strength polypropylene resin is less than 16,000 kgf / cm ² , heat resistance and abrasion resistance may be deteriorated.

The content of the high melt strength polypropylene resin is preferably 5 to 30% by weight, more preferably 10 to 20% by weight based on the total resin composition. When the content of the high melt strength polypropylene resin is less than 5% by weight, it may be difficult to obtain the effect of improving wear resistance and melt tension, and when the content exceeds 30% by weight, the flowability of the resin may be lowered and the workability may be lowered.

As described above, the polypropylene resin composition of the present invention can effectively mix a high crystalline α-olefin-propylene copolymer and a high melt strength polypropylene resin to ensure excellent rigidity and wear resistance, and to provide high crystalline α-olefin-propylene air. In the case of using a composition composed only of coalescence, sufficient physical properties for the production of caps for carbonated drinks and juice containers cannot be secured, and in the case of using a composition composed of only high melt resin, the fluidity of the product itself becomes difficult. .

Meanwhile, the polypropylene resin composition of the present invention may further include (C) a nucleating agent, for example, an organic nucleating agent or an inorganic nucleating agent, to improve the rigidity, heat resistance, and crystallization rate of the polypropylene.

As the nucleating agent, one or more organic nucleating agents such as sorbitol-based compounds and phosphide-based bismuth-based compounds and inorganic nucleating agents such as talc can be selected and used. At this time, more preferably, it is possible to significantly improve the rigidity and effectively reduce the crystallization rate by using a phosphine-based phosphide-based compound.

The content of the nucleating agent is preferably 0.05 to 0.3 parts by weight based on 100 parts by weight of the total of the (A) highly crystalline α-olefin-propylene copolymer and (B) the high melt strength polypropylene resin, and is sufficient when the content is less than 0.05 parts by weight. The expression of heat resistance and crystallization rate is lowered, and when it exceeds 0.3 parts by weight, no further improvement in physical properties is seen.

The polypropylene resin composition of the present invention comprises (A) 70 to 95% by weight of a high crystalline α-olefin-propylene copolymer having an isotactic index (II) of 97% or more, and (B) a high melt strength polypropylene resin. 5 to 30% by weight, and 0.05 to 0.3 parts by weight of nucleating agent is added to 100 parts by weight of the total of (C) the above-mentioned (A) highly crystalline α-olefin-propylene copolymer and (B) the high melt strength polypropylene resin. It can be to include.

In addition, a neutralizing agent, an antioxidant, an antistatic agent, a slip agent, an antiblocking agent, a pigment, or an inorganic agent, which are commonly used, may be added to the polypropylene resin composition of the present invention.

On the other hand, the present invention provides a molded article prepared from the polypropylene resin composition.

Molded articles made of the composition has excellent heat resistance and abrasion resistance, the rate of snow formation that can occur during continuous extrusion of the cap is drastically reduced, and can prevent deformation of the cap during sterilization of juice at high temperatures, so that the cap for carbonated drinks and juice containers It can be effectively used as a material.

In particular, the molded article of the present invention may be a plastic cap for carbonated beverages or juice containers.

The molded article of the present invention has a flexural modulus of 18,000 kgf / cm ² to 18,100 kgf / cm ² according to ASTM evaluation method D790, and an impact strength of 9.4 kg? Cm / cm to 9.5 kg? Cm / cm according to ASTM evaluation method D256, ASTM The TABER index according to Evaluation Method D1175 may be 0.096 to 0.111.

The molded article can be effectively used as a plastic cap material for carbonated beverages and juice containers with excellent stiffness and wear resistance by securing improved flexural modulus, impact strength, and TABER index.

In the present invention, matters other than those described above can be added or subtracted as required, and therefore, the present invention is not particularly limited thereto.

The present invention can provide a polypropylene resin composition for plastic caps excellent in heat resistance and abrasion resistance by mixing and using a high crystalline α-olefin-propylene copolymer with a high melt strength resin.

In addition, the polypropylene resin composition according to the present invention can be effectively used in the production of heat-resistant caps, pressure-resistant caps using an extrusion molding process.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the following examples.

First, in Examples 1 to 2 and Comparative Examples 1 to 3, physical properties of each copolymer, resin, and polypropylene composition are as follows.

1) Melt index: measured at 230 ° C. with a 2.16 kg load according to ASTM Evaluation Method D1238.

2) Izod impact strength: Notched injection specimens were measured at 23 ° C. and 50% relative humidity according to ASTM Evaluation Method D256.

3) Flexural modulus: Injection specimens were measured at 23 ° C. and 50% relative humidity according to ASTM Evaluation Method D790.

4) Heat Deflection Temperature: Injection specimens were measured at 4.6 kg.f load according to ASTM Evaluation Method D648.

5) Crystallization temperature: The temperature rising rate was measured by using a DSC equipment at 10 ℃ / min.

6) Abrasion resistance evaluation: The sample was rotated (1,000 times) while a predetermined load (1,000 g) was applied by a prescribed abrasive stone to measure abrasion through weight loss of the sample, and the TABER index was calculated according to the following Equation 1.

The equipment standard was made based on JIS A 1453, K 6902, K 7204, ASTM D 1175, D 1044, and measured according to the above evaluation criteria.

[Calculation 1]

TABER index = (standard speed) / (test speed) × loss weight (mg)

Manufacturing example : High crystallinity  Preparation of α-olefin-propylene copolymer

Propylene was added to the polymerization reactor, triethylaluminum, a phthalate catalyst imparting high crystallinity, and a silane-based electron donor were injected, and the slurry bulk polymerization was carried out at a reaction temperature of 65 to 75 ° C. and 32 to 34 atmospheres to obtain isotactic index 99. A high crystalline polypropylene homopolymer (%) was prepared, followed by copolymerization with ethylene to prepare a high crystalline α-olefin-propylene copolymer having an α-olefin content of 6% by weight, and the melt index was 8.0 g / 10min with hydrogen. Adjusted.

Example  1-2

As shown in Table 1, after mixing the high crystalline α-olefin-propylene copolymer A and the high melt strength polypropylene resin B1 with different compositions and content ratios to prepare a polypropylene composition, the phosphate phosphide-based compound ( Manufacturer: ADEKA) was added in an amount of 0.2 parts by weight based on 100 parts by weight of the total composition, mixed for 3 minutes in a Hansel mixer, and extruded by a twin screw extruder at 170 to 220 ° C. to obtain a pellet-like polypropylene resin composition.

Comparative example  1-3

A polypropylene resin composition was prepared in the same manner as in Examples 1 and 2, except that the composition was performed as shown in Table 3 below.

division A
(weight%) B1
(weight%) B2
(weight%) B3
(weight%) C
(Parts by weight) Example 1 90 10 - - 0.2 Example 2 85 15 - - 0.2 Comparative Example 1 100 - - - 0.2 Comparative Example 2 90 - 10 - 0.2 Comparative Example 3 90 10 0.2 A: highly crystalline α-olefin-propylene copolymer (melt index 8.0 g / 10min (230 ° C., 2.16 kg load), α-olefin content 6 wt%, isotactic index 99%
B1: high melt strength polypropylene resin (stretching degree 66, melt index 1.8 g / 10min, flexural modulus 18,000 kgf / cm ² )
B2: polypropylene homopolymer (melt index 1.0 g / 10 min, isotactic index 95%
B3: α-olefin-propylene copolymer (melt index 1.8 g / 10min, α-olefin content 6 wt%, isotactic index 95%
C: organic type nucleating agent (phosphoric acid svir type compound)

Experimental Example

The pelletized polypropylene resin composition prepared according to Examples 1 to 2 and Comparative Examples 1 to 3 was injected into an LS electric wire 140 ton molding machine to prepare a test piece for measuring physical properties of a plastic cap material for carbonated beverages or juice containers. Specimens were made with a press molding machine.

For each specimen thus prepared, the physical properties were measured in the same manner as described above, and the measurement results thereof are shown in Table 2 below.

division Melt Index
(g / 10 min) Flexural modulus
(kg.f / cm ² ) Izod
Impact strength
(kg? cm / cm) Crystallization temperature
(℃) Crystallization time
(sec) TABER Index Example 1 9.3 18,100 9.4 130.6 84.6 0.111 Example 2 9.1 18,000 9.5 130.5 84.1 0.096 Comparative Example 1 9.5 18,100 8.9 130.3 93.1 0.145 Comparative Example 2 8.2 18,200 9.0 130.2 92.4 0.122 Comparative Example 3 8.8 17,900 8.9 130.5 91.4 0.105

As shown in Table 2, the polypropylene compositions of Examples 1 to 2 comprising (A) a highly crystalline α-olefin-propylene copolymer and (B) a high melt strength polypropylene resin according to the present invention have a flexural modulus. 18,000 kgf / cm ² to 18,100 kgf / cm ² and the impact strength is from 9.4 kg cm / cm / cm to 9.5 kg cm / cm showing improved stiffness and impact strength.

On the other hand, Comparative Examples 1 to 3, which consist of only a high crystalline α-olefin-propylene copolymer, retained similar stiffness as compared with Examples 1 to 2, but the impact strength was from 8.9 kg? Cm / cm to 9.0 kg? Cm / cm. It can be seen that the fall significantly. When the impact strength is lowered, cracks may occur in the final manufactured molded product, and thus it may be difficult to maintain airtightness as a plastic cap material for carbonated beverages and juice containers.

On the other hand, the polypropylene composition of Examples 1 to 2 has a crystallization time of 84.1 sec to 84.6 sec, significantly shorter than the crystallization time of the composition according to Comparative Examples 1 to 3 is 91.4 to 93.1, excellent in the actual manufacturing process It can be seen that significant productivity gains can be achieved.

In addition, even in the measurement of wear resistance, the TABER index for Examples 1 to 2 is 0.096 to 0.111, and it can be seen that the TABER index related to Comparative Examples 1 to 3 has very good wear resistance compared to 0.105 to 0.145. In the case where the wear resistance is remarkably inferior as in Comparative Examples 1 to 3, there is a problem in that productivity is likely to occur due to the high possibility of generating snow powder in the mold during continuous cap molding.

As described above, it was confirmed that the resin which effectively blended the high crystalline α-olefin-propylene copolymer with the high melt resin was maintained the stiffness, the impact strength is improved, and the wear resistance is remarkably improved. It can be seen that significant productivity improvements can be made.

Claims (14)

(A) 70 to 95% by weight of a highly crystalline α-olefin-propylene copolymer having an Isotactic Index (I.I) of 97% or more, and (B) 5 to 30% by weight of high melt strength polypropylene resin Polypropylene resin composition comprising a. The method of claim 1, (A) The polypropylene resin composition having an α-olefin content of 4 to 8% by weight of the highly crystalline α-olefin-propylene copolymer. The method of claim 1,  (A) The polycrystalline resin composition having a high crystalline α-olefin-propylene copolymer having a melt index of 2 to 10 g / 10 min. The method of claim 1, (A) The polypropylene resin composition whose isotactic index (I.I, Isotactic Index) of a high crystalline alpha-olefin-propylene copolymer is 99% or more. The method of claim 1, (B) The high melt strength polypropylene resin is a polypropylene resin composition having a melt index of 0.3 to 10 g / 10 min. The method of claim 1, (B) The high melt strength polypropylene resin has a polypropylene resin composition having a strain hardening index (SHI) of 30 or more. The method of claim 1, (B) The high melt strength polypropylene resin has a flexural modulus of 16,000 kgf / cm ² to 20,000 kgf / cm ² or more. The method of claim 1, The content of (A) the high crystalline α-olefin-propylene copolymer is 80 to 90% by weight based on the total resin composition, and (B) the content of the high melt strength polypropylene resin is 10 to 20% by weight based on the total resin composition. Polypropylene resin composition. The method of claim 1, The polypropylene resin composition which further contains 0.05-0.3 weight part of (C) nucleating agent with respect to a total of 100 weight part of said (A) high crystalline alpha-olefin-propylene copolymers, and (B) high melt strength polypropylene resin. 10. The method of claim 9, (C) The polypropylene resin composition in which the nucleating agent is at least one member selected from the group consisting of sorbitol compounds, phosphates phosphates, and talc. 10. The method of claim 9, (A) 70 to 95% by weight of a highly crystalline α-olefin-propylene copolymer having an Isotactic Index (I.I) of 97% or more, and (B) 5 to 30% by weight of high melt strength polypropylene resin, (C) A polypropylene resin composition further comprising 0.05 to 0.3 parts by weight of the nucleating agent, based on 100 parts by weight of the total of the (A) high crystalline α-olefin-propylene copolymer and (B) the high melt strength polypropylene resin. A molded article prepared from the polypropylene resin composition according to any one of claims 1 to 11. The method of claim 12, Molded plastic caps for carbonated beverages or juice containers. The method of claim 12, Flexural modulus according to ASTM evaluation method D790 is 18,000 kgf / cm ² to 18,100 kgf / cm ² , impact strength according to ASTM evaluation method D256 is 9.4 kg? Cm / cm to 9.5 kg? Cm / cm, and TABER according to ASTM evaluation method D1175 Molded articles having an index of 0.096 to 0.111.